Zookeeper源码环境搭建
Zookeeper是开源高可用的分布式协同服务，在分布式系统中应用广泛，代码量适中，适合阅读和学习。首先从开发环境的搭建开始介绍。
源码获取
Zookeeper源码Github地址https://github.com/apache/zookeeper
Zookeeper官网（Apache）https://zookeeper.apache.org/releases.html
Zookeeper在3.5.5之前使用的是Ant构建，在3.5.5开始使用的是Maven构建。
工程结构
| 名称 | 说明 |
|---|---|
| bin | 包含访问zookeeper服务器和命令行客户端的脚本 |
| conf | 启动zookeeper默认的配置文件目录 |
| zookeeper-assembly | 基础服务打包目录。 |
| zookeeper-client | 客户端，目前只支持c。 |
| zookeeper-compatibility-tests | 兼容性测试目录。 |
| zookeeper-contrib | 附加的功能,比如zookeeper可视化客户端工具。 |
| zookeeper-doc | zookeeper文档。 |
| zookeeper-it | 供fatjar使用，进行系统测试依赖的类 |
| zookeeper-jute | zookeeper序列化组件。 |
| zookeeper-metrics-providers | 监控相关，目前支持普罗米修斯 prometheus。 |
| zookeeper-recipes | zookeeper提供的一些功能例子，包括选举election，lock和queue。 |
| zookeeper-server | zookeeper服务端。 |
启动服务
maven执行install
运行命令：mvn -DskipTests clean install -U
构建信息
[INFO] Apache ZooKeeper [pom]
[INFO] Apache ZooKeeper - Documentation [jar]
[INFO] Apache ZooKeeper - Jute [jar]
[INFO] Apache ZooKeeper - Server [jar]
[INFO] Apache ZooKeeper - Client [pom]
[INFO] Apache ZooKeeper - Recipes [pom]
[INFO] Apache ZooKeeper - Recipes - Election [jar]
[INFO] Apache ZooKeeper - Recipes - Lock [jar]
[INFO] Apache ZooKeeper - Recipes - Queue [jar]
[INFO] Apache ZooKeeper - Assembly [pom]
注：建议跳过test，不然需要很长时间，另外有些包是provider的，在打包时候不会打进去，所以需要改下，不然启动的时候会报class not found，这些依赖如下：
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-server</artifactId>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-servlet</artifactId>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<scope>provided</scope>
</dependency>
启动入口
zk服务端的启动入口是QuorumPeerMain类中的main方法
如果不配置的话，无法输出日志
VM options：
-Dlog4j.configuration=file:conf\log4j.properties
单机版启动需要参数
Program arguments：
conf\zoo_sample.cfg
启动成功后的日志
[main:QuorumPeerConfig@136] - Reading configuration from: D:\Github\zookeeper\conf\zoo_sample.cfg
[myid:] - WARN [main:VerifyingFileFactory@59] - \tmp\zookeeper is relative. Prepend .\ to indicate that you're sure!
[myid:] - INFO [main:QuorumPeerConfig@388] - clientPortAddress is 0.0.0.0:2181
[myid:] - INFO [main:QuorumPeerConfig@392] - secureClientPort is not set
[myid:] - INFO [main:DatadirCleanupManager@78] - autopurge.snapRetainCount set to 3
[myid:] - INFO [main:DatadirCleanupManager@79] - autopurge.purgeInterval set to 0
[myid:] - INFO [main:DatadirCleanupManager@101] - Purge task is not scheduled.
[myid:] - WARN [main:QuorumPeerMain@125] - Either no config or no quorum defined in config, running in standalone mode
[myid:] - INFO [main:ManagedUtil@45] - Log4j 1.2 jmx support found and enabled.
[myid:] - INFO [main:QuorumPeerConfig@136] - Reading configuration from: D:\Github\zookeeper\conf\zoo_sample.cfg
[myid:] - WARN [main:VerifyingFileFactory@59] - \tmp\zookeeper is relative. Prepend .\ to indicate that you're sure!
[myid:] - INFO [main:QuorumPeerConfig@388] - clientPortAddress is 0.0.0.0:2181
[myid:] - INFO [main:QuorumPeerConfig@392] - secureClientPort is not set
[myid:] - INFO [main:ZooKeeperServerMain@118] - Starting server
......
[myid:] - INFO [main:Server@415] - Started @1399ms
[myid:] - INFO [main:JettyAdminServer@116] - Started AdminServer on address 0.0.0.0, port 8080 and command URL /commands
[myid:] - INFO [main:ServerCnxnFactory@135] - Using org.apache.zookeeper.server.NIOServerCnxnFactory as server connection factory
[myid:] - INFO [main:NIOServerCnxnFactory@673] - Configuring NIO connection handler with 10s sessionless connection timeout, 2 selector thread(s), 32 worker threads, and 64 kB direct buffers.
[myid:] - INFO [main:NIOServerCnxnFactory@686] - binding to port 0.0.0.0/0.0.0.0:2181
[myid:] - INFO [main:ZKDatabase@117] - zookeeper.snapshotSizeFactor = 0.33
[myid:] - INFO [main:FileTxnSnapLog@404] - Snapshotting: 0x0 to \tmp\zookeeper\version-2\snapshot.0
[myid:] - INFO [main:FileTxnSnapLog@404] - Snapshotting: 0x0 to \tmp\zookeeper\version-2\snapshot.0
[myid:] - INFO [ProcessThread(sid:0 cport:2181)::PrepRequestProcessor@132] - PrepRequestProcessor (sid:0) started, reconfigEnabled=false
[myid:] - INFO [main:ContainerManager@64] - Using checkIntervalMs=60000 maxPerMinute=10000
[myid:] - INFO [SyncThread:0:FileTxnLog@218] - Creating new log file: log.1
